Ronald Reagan came to one of the nation's most prosperous farm areas today to decry "unprecedented disaster" in Carter administration agricultural policies and cautiously promise to "work toward the goal of achieving full parity" for the American farmer.

Reagan spoke at a showcase corn-and-livestock farm in an area where farm exports are up 25 percent even though corn production has been damaged somewhat by drought. His message to farmers was that President Carter had all but wrecked the family farm and imposed a grain embargo on the Soviet Union that was "grandstanding for the American people at your expense."

To the farm of Iowa's secretary of agriculture, Robert Lounsbery, Reagan brought a list of past proposals -- all wrapped into what spokesman Lyn Nofziger called "probably our definitive farm speech."

The Republican nominee called for "aggressive expansion" of agricultural imports and of the Food for Peace program, for development of fuel farming and for repeal of estate taxes.

"I promise to give farm exports direct, personal, presidential support [and] to insist that access to farm markets be kept free of unreasonable trade barriers," Reagan said.

Reagan's reference to "parity," a fair-income measurement based on 1910-14 farm prices, was deliberately vague.

"And when we get this economy back on track again and get control of killer inflation, farmers can have a vigorously strong marketplace in which they can work for the goal of full parity," Reagan said, adding. "There are some who didn't think I'd use that word."

Campaigning in Kansas during the GOP primaries, Reagan appeared not to be familiar with the word "parity." He afterward acknowledged that he hadn't wanted to talk about his own historic opposition to farm price supports, causing Kansas Sen. Bob Dole to quip that Reagan believed in "faith, hope and parity."

Reagan subsequently made clear that he supported "parity" not in the technical sense as it relates to farm income but only in the broad meaning of "fairness" to farmers.

Reagan made today's speech in the tree-shaded farmyard in front of a well-stocked grain silo which was draped with a huge banner greeting him. Other signs on the farm advertised a forthcoming hog roast at which the featured speaker will be Earl Butz, a secretary of agriculture in the Nixon and Ford administrations.

The signs advertising the hog roast said that "Mr. Butz is sharp, witty and straight on the issues. Don't pass this one."

Former national Republican chairman Mary Louise Smith, now the GOP national committeewoman from Iowa, told reporters that Reagan has "a solid lead" over President Carter in Iowa. Gerald Ford narrowly captured the state's eight electoral votes in 1976.

From Iowa, Reagan flew to New York City for a speech at a Republican fund-raising dinner.

At New York's La Guardia airport, Reagan was asked about his historic opposition to the federal bailout of New York City. He replied that he had been in favor of federal loan guarantees ever since Mayor Ed Koch was elected and showed that he could "straighten out" the city's financial situation.

Koch was elected mayor in 1977. Reagan opposed a federal bailout until January 1980.